In the field of microelectronic devices and sensors, the development of devices that are small relative to the state of the art, conveniently and relatively inexpensively reproduced, and produced with a relatively low failure rate has long been important. In the fields of cellular and developmental, and molecular biology, microbiology, biomedical devices, and biotechnology, there is now a growing need for devices of similar scale with features as small as or smaller than individual cells.
In the electronics industries, such devices have been produced by a variety of methods. A well-known method of production of such devices is photolithography. According to this technique, a thin film of conducting, insulating, or semiconducting material is deposited on a substrate and a negative or positive resist (photoresist) is coated onto the exposed surface of the material. The resist is then irradiated in a predetermined pattern, and irradiated (positive resist) or non-irradiated (negative resist) portions of the resist are washed from the surface to produce a predetermined pattern of resist on the surface. Alternatively, micromachining has been employed to mechanically remove small areas from a surface to form a pattern.
While the above-described irradiative lithographic methods may be advantageous in many circumstances, all require relatively sophisticated and expensive apparatus to reproduce a particular material pattern on a plurality of substrates, and are relatively time-consuming. Additionally, no method of patterning other than on a flat substrate is commonly available according to the methods.
These techniques have recently been employed in the biological sciences to create patterned surfaces on which cells may be adhered and grown. For example, the orientation, spreading, and shape of several cell types have been shown to be affected by topography. Thus cells have been grown on grooved surfaces which have been created by micromachining surfaces or by using photolithography to etch away parts of surfaces. (See, for example, D. M. Brunette, Exp. Cell Res., 167:203-217, 1986; T. Inoue, et al., J. Biomedical Materials Res., 21:107-126, 1987; B. Chehroudi, et al., J. Biomedical Materials Res., 22:459-473, 1988; G. A. Dunn and A. F. Brown, J. Cell Sci., 83:313-340, 1986; A. Wood, J. Cell Sci., 90:667-681, 1988; B. Chehroudi, et al., J. Biomedical Materials Res., 24-1203-1219, 1990; P. Clark, et al. Development, 99:439-448, 1987.
A need exists in the art for a convenient, inexpensive, and reproducible method of plating or etching a surface according to a predetermined pattern. The method would ideally find use on planar or nonplanar surfaces, and would result in patterns having features in the submicron domain. Additionally, the method would ideally provide for convenient reproduction of existing patterns.
The study of self-assembled monolayers (SAMs) is an area of significant scientific research. Such monolayers are typically formed of molecules each having a functional group that selectively attaches to a particular surface, the remainder of each molecule interacting with neighboring molecules in the monolayer to form a relatively ordered array. Such SAMs have been formed on a variety of substrates including metals, silicon dioxide, gallium arsenide, and others. SAMs have been applied to surfaces in predetermined patterns in a variety of ways including simple flooding of a surface and more sophisticated methods such as irradiative patterning.
Monolayers may be produced with varying characteristics and with various functional groups at the free end of the molecules which form the SAM. Thus, SAMs may be formed which are generally hydrophobic or hydrophilic, generally cytophobic or cytophilic, or generally biophobic or biophilic. Additionally, SAMs with very specific binding affinities can be produced. This allows for the production of patterned SAMs which will adhere cells, proteins, or other biological materials in specific and predetermined patterns.
Accordingly, a general purpose of the present invention is to provide a method of conveniently and reproducibly producing a variety of SAM patterns on planar as well as nonplanar surfaces, the patterns having resolution in the submicron domain and being capable of adhering cells, proteins, or other biological materials in specific and predetermined patterns. Another purpose of the invention is to provide a method of forming a template from an existing pattern having micron or submicron-domain features, the template conveniently reproducing the pre-existing pattern.